It can be hard to find information on private companies as they only report to the IRS and that information is not public.
Industry Ratios are a great way to evaluate your company's or any company's performance with industry averages. These are the best industry ratio resources:
Electronic:
Paper
Tip: Many company databases (public/private) will give some ratios.
News sources such as magazines, journals, newspaper, business journals, and company web sites can be excellent sources of information such as sales figures, number of employees, new customers, and major events. Look for quotes by officers or industry insiders.
Public company databases get their information from the required filings that companies must make to the SEC. Information is only updated when filings are done. One nice feature of these databases is they allow you to pull up a list of companies in the same industry using either SIC or NAICS Codes.